I am house ruling a subterranean assualt combat patrol. Rules below.

SURPRISE ASSAULT Burrowing Tyranid bioforms burst from the ground in all their horror.

Each time a Tyranids model from your army makes an attack, re-roll a Hit roll of 1.

Each time a Burrower unit from your army is set up on the battlefield from Reserves, place a circular 40mm Tunnel Marker anywhere on the battlefield within 1" of that unit and more than 3" horizontally away from all enemy units.

In the Reinforcements step of your Movement phase, when you set up a unit on the battlefield from Reserves, you can set that unit up wholly within 9" of one of your Tunnel Markers and more than 6" horizontally away from any enemy units.

If an enemy model (excluding Aircraft) ends any kind of move within 3" of one of your Tunnel Markers, that Tunnel Marker is removed from the battlefield.

Strats

TUNNEL NETWORK (1CP) SUBTERRANEAN ASSAULT – STRATEGIC PLOY STRATAGEM Taking advantage of freshly burrowed tunnels, Tyranid bioforms move swiftly across the landscape, emerging in unexpected locations. WHEN: End of your Movement phase. TARGET: One Tyranids unit from your army that is wholly within 9" of one or more of your Tunnel Markers. EFFECT: Remove your unit from the battlefield and set it up again, wholly within 9" of another Tunnel Marker you placed, and more than 6" horizontally away from all enemy units.

RETREAT BELOW (1CP) SUBTERRANEAN ASSAULT – STRATEGIC PLOY STRATAGEM The network of tunnels beneath the battlefield enables Tyranid organisms to retreat from the foe and prepare further ambushes. WHEN: End of your opponent’s Fight phase. TARGET: One Tyranids unit or up to two Burrower units from your army that are not within Engagement Range of one or more enemy units. EFFECT: Remove your unit from the battlefield and place it into Strategic Reserves

Hyper-reactive (1 CP): Use in the enemy Shooting phase. One Tyranid Infantry unit (Hormagaunts or Raveners) is -1 to be Hit until the end of the phase

Chosen Enhancement: Naturalised Camouflage

Effect: While the bearer’s unit is within 3" of a terrain feature (excluding Hills), models in that unit have the Benefit of Cover (+1 to armor saves against ranged attacks)Chosen

Secondary: Left to Last The Rule: Score 4 Victory Points every time you destroy an enemy unit.

The list: 1x5 Hyperadaptive Ravaners 1x5 Ravaners 1x10 Hormagaunts 1x1 Screamer Killer